The word “cooking” implies that you heat things up. But how much? Clearly the
temperature is important.

By comparison with other technical issues around cooking, temperatures are relatively
straightforward. There's the Celsius scale (water freezes at 0° and boils at 100°), and the
Fahrenheit scale (water freezes at 32° and boils at 212°). The obsolete Réamur scale and
the technical Kelvin scale are not used in cooking. Celsius is still frequently referred to
as Centigrade, since it has 100 degrees between freezing and boiling.

Fahrenheit gets on my nerves because I'm not used to it, but it's relatively easy to convert
to Celsius: C = (F - 32) * 5 / 9. When I feel like it, I might include a conversion table
here.

But how do you measure temperatures? In days gone by, you guessed, probably based on some
related factor like surface colour or the length of time cooking. Both are not very good
indications, but with practice you can get things right, at least until you change some
parameter. If you need 50 minutes to cook a 2 kg chicken in the oven at a specified
temperature marking (ovens vary wildly in the accuracy of their thermostats), how
long do you cook a 3 kg chicken? Or how long do you cook it in a different oven?

Clearly there has to be a better solution, and there is: measure the temperature where
you're interested in it, inside the food (usually meat), with a thermometer. There are
two main issues with meat thermometers: the devices available, and how to use them: what
temperature are you aiming for, and where? No object warms up completely evenly, and if
you measure the right temperature in the wrong place, there's a good chance that the
results won't be what you want.

The devices

Meat thermometers have been around for a while. The older ones are analogue, usually with a
dial, though I've seen glass ones filled with spirits. Mercury is poisonous, and there's a
danger of a thermometer breaking in the meat; that's probably one reason for the dial-type
thermometers. The ones I have found in Australia recently have left much to be desired.
Some are even made of plastic (“do not place in the oven”). The best I've found
looks like this:

The scale is in Fahrenheit, with Celsius conversions (66, 71, and other unlikely values).
The best thing about it is the warning at the bottom: Do not put in water. My old
thermometer, made in Germany, does not have this inscription:

But at least this thermometer has a scale in Celsius, and it's relatively fine-grained (even
if it is off by nearly 10°; but you can compensate for that sort of thing). It also has a
much smaller sensor, which is good for the food:

It's useful (and not overly expensive), but it's not easy to use. The temperature probe (in
front) is coated with metal, and it is connected with a wire braid. I presume that the
sensor itself is at the tip of the probe, but the metal cover is a good conductor of heat,
and as a result it tends to show higher temperatures than you'd expect. That's why I've
wrapped some stiff paper around it, to insulate it from the outside. A ceramic covered
probe would be much better. It would also have avoided the fate of this particular unit: I
put the probe in a barbecue with the lid down, and it fried the probe (presumably the
cable). But I needed to find a better unit anyway.

The next one I bought was from IKEA. It looks
quite similar to one illustrated in Bonniers Kokbok.
Maybe it's a relatively common design in Sweden:

It doesn't seem to have the same issues as my first digital thermometer, and it has a magnet
on the back that makes it possible to attach it to the fridge next to the oven. About the
only issues I have with it is that the sensor is rather slow to react, and that you can't
turn off the beeping it makes when you hit the set temperature.

Cooking temperatures

What temperature should a roast beef be in the middle? Ask me and I'd say 58°. Ask others
and they might come up with something else, assuming they know any temperature at all. The
Americans seem to be particularly keen on higher temperatures— Wikipedia includes an
“updated temperature” column which effectively redefines such terms as
“medium rare” and “rare”, apparently based on a “fact
sheet” from the US Department
of Agriculture. What good that does is beyond me. Possibly it's the US equivalent of
our bad language. Other US sites are more
reasonable, though for some reason it gives higher temperatures for lamb than for beef.

One important example where temperature control is cooking whole chickens. Underdo them and
the thigh meat is still red, and it's difficult to get it off the bone. Overdo them and the
breast turns to cardboard.

But what temperature? Where do you measure it? The canonical answer, and the one that I
found in the only two cookbooks I have that mention such things, is in the thighs, where the
chicken cooks the slowest. Bonniers Kokbok recommends a
temperature of 70°. The other one (I forget which, but it was English or Australian as
opposed to US American) specifies 75-80°. The about.com page recommends
165° to 175°F, or between 74° and 79°, but doesn't say where.
The problem is that I've tried this before (in
fact, going to 88°, which is what I recall from the charts on my old analogue thermometers),
and I continually got underdone thighs.

I've decided that the real issue is the exact placing of the probe, and possibly the fact
that it's not specific enough, and the thermometer is too influenced by the temperatures of
the looser space around the bone, which gets cooked first. Today I decided to measure in the
breast. There are a couple of reasons: first, it's larger, so the danger of incorrect
readings is less, and secondly, it's the most likely to be overdone. I took it out at
82°, and the results were much better, but still not quite enough. I'll try 88° in the
breast next time.